The present invention relates to an electric catheter for the electrotherapy or examination of cardiac tissue, i.e., of myocardium. On its proximal end, the electrode catheter has a terminal, using which the electrode line is connected to an electrical generator, an electrotherapy device, or even to an implant, such as a cardiac pacemaker or defibrillator. The therapy device is preferably a generator for high-frequency current for tissue ablation. On its distal end, the electrode catheter has one or more sensing electrodes or, additionally or alternatively, treatment electrodes.
Electrode catheters of this type are known in particular in the field of electric physiology for detecting and treating stimulus conduction malfunctions in the heart and are also referred to as EP catheters (electrophysiology catheters). In the present case, this name is to include both mapping catheters for detecting myocardial stimulus conduction or ablation catheters for the local erosion of cardiac tissue (myocardium) or combinations of such electrode catheters. Such electrode catheters are used for the purpose of detecting the excitation propagation in the myocardium with the aid of sensing electrodes in a first step, in order to be able to recognize malfunctions of the excitation propagation in this way. Subsequently, by applying typically high-frequency AC current, which may be output in a targeted way via treatment electrodes, tissue erosion (ablation) may be caused, with the result that stimulus conduction no longer occurs where the cardiac tissue is eroded.
Corresponding catheters and treatments are known in principle and have had the great disadvantage up to this point that the treatment cannot be performed under observation in the course of magnetic resonance tomography, since the electrical lines between the proximal end of the electrode catheter and the electrodes at the distal end of the electrode catheter may heat up significantly as a result of induction currents induced by the magnetic resonance tomography. In addition, the electrical conductors of the typical electrode catheters result in undesired artifacts in the image recorded using magnetic resonance tomography.
This problem is all the greater since the maximum power consumption of the electrical lines is given when their length is a multiple of half of the wavelength output by the magnetic resonance tomograph, i.e.,
      λ    2    .This condition is fulfilled in typical electrical lines of typical EP catheters. A further difficulty is that the greatest heating occurs precisely in proximity to the distal end of the corresponding electrode catheter in the area between endocardium and myocardium.
Up to this point, these reasons have resulted in electrophysiological examination of the myocardium or electrotherapy of the myocardium in the form of ablation or similar treatments not being able to be performed under observation in magnetic resonance tomographs.
Similar problems also result in connection with stimulation electrode catheters or defibrillation electrode catheters for connection to an implantable cardiac pacemaker, cardioverter, defibrillator, or the like. Since typical defibrillation and stimulation electrode catheters are not compatible with magnetic resonance, the patients having such implants may not be examined using a magnetic resonance tomograph.
The object of the present invention is therefore to provide an electrode catheter which also allows use in magnetic resonance tomographs.
This object is achieved according to the present invention by an electrode catheter of the type cited at the beginning, in which the electrical conductor(s) running from the proximal to the distal ends of the electrode catheter is/are made of carbon.
It has been shown that, using electrical conductors made of carbon, both the undesired effect of heating of the electrical conductors because of alternating magnetic fields in the currents induced in magnetic resonance tomographs and also the undesired effect of artifacts in magnetic resonance tomographs may be avoided.
Interestingly, electrode catheters for connection to a cardiac pacemaker are known from each of US patents U.S. Pat. Nos. 4,467,817, 4,721,118 and 4,585,013, in which the electrical conductors between the proximal end connected to the cardiac pacemaker and the distal end located in the heart are made of carbon fibers, which are provided in the form of a bundle in a multiple of approximately 3000 high modulus filaments. These electrode catheters are to achieve the object of providing an electrode catheter having the smallest possible diameter. There is no indication in the publications that electrode catheters for electrophysiology, in particular ablation electrode catheters, may be constructed similarly, or that electrode catheters having an electrical conductor made of carbon fibers permit use or observation in the framework of magnetic resonance tomography.